Title: Assessment of Vitamin and Carotenoid Concentrations of Emerging Food Products: Edible Microgreens
Authors: Zhenlei Xiao, Gene E. Lester, Yaguang Luo, and Qin Wang
Published: July 18, 2012
Epidemiological studies have shown that fruit and vegetable consumption is associated with reduction in the development of chronic disease, such as cancer and cardiovascular disease.1,2 Diets rich in fruits and vegetables provide an abundance of human bioactive compounds,3 such as ascorbic acid (vitamin C), carotenoids (provitamin A compounds), phylloquinone (vitamin K1), and tocopherols (vitamin E), which are known to have protective benefits against cancers and cardiovascular disease.4 The new Dietary Guidelines for Americans (2010) released by the U.S. Department of Agriculture (USDA) and the Department of Health and Human Services (DHHS) specifically recommends Americans to fill half of their plate with fruits and vegetables because they possess benefits for human health. Microgreens are an exotic genre of edible greens, appearing in upscale markets and restaurants, that have gained popularity as a new culinary trend over the past few years. Microgreens are tender immature greens produced from the seeds of vegetables and herbs, having two fully developed cotyledon leaves with or without the emergence of a rudimentary pair of first true leaves. Microgreens are usually 2.5−7.6 cm (1−3 in.) in height, harvested at 7−14 days after germination, depending on the species, and sold with the stem and attached cotyledons (seed leaves). Although small in size, microgreens can provide a large array of intense flavors, vivid colors and tender textures. Therefore, microgreens can be served as a new ingredient in salad, soups, and sandwiches, enhancing their color, texture, and/or flavor, and also can be used as edible garnish to brighten up a wide variety of main dishes.5−8 Although microgreens have been claimed as nutritionally beneficial, to the best of our knowledge, no scientific data are available on the exact phytochemical content of microgreens. Limited studies have shown that some young seedlings may have much higher levels of vitamins, minerals, and other health giving phytonutrients than the mature leaves. In a recent study from Lester et al.,9 it was reported that the younger leaves of baby spinach (Spinacia oleracea L.) generally had higher levels of phytonutrients: vitamins C, B9 and K1, and the carotenoids (lutein, violaxanthin, zeaxanthin and β-carotene) than the more mature leaves. Oh et al.10 also found that young lettuce (Lactuca sativa) seedlings, 7 days after germination, had the highest total phenolic concentration and antioxidant capacity in comparison to the older leaves. Therefore, the object of this study was to assess the vitamin and carotenoid concentrations of the 25 commercially available varieties of microgreens. The human bioactive compounds assayed include ascorbic acid (total, free, and dehydro), carotenoids (β-carotene, violaxanthin, and lutein/zeaxanth
In summary, the essential vitamin and carotenoid concentrations of 25 commercially available microgreens varieties have been determined. In general, microgreens contain considerably higher concentrations of vitamins and carotenoids than their mature plant counterparts, although large variations were found among the 25 species tested. Maximum values of vitamin C, vitamin K1, and vitamin E were found in red cabbage, garnet amaranth, and green daikon radish microgreens, respectively. In terms of carotenoids, cilantro microgreens showed the highest concentration of lutein/zeaxanthin and violaxanthin and ranked second in β-carotene concentration. In contrast, popcorn shoots and golden pea tendrils were relatively low in vitamins and carotenoids, although they were still comparable nutritionally to some commonly consumed mature vegetables. It is also noted that golden pea tendrils, which are grown in the absence of light, processed much lower vitamin and carotenoid concentrations than pea tendrils grown under light, suggesting that light plays an important role on nutritional values during the growth of microgreens. The data generated by this research likely provide a scientific basis for evaluating the vitamin and carotenoid concentrations of microgreen cotyledon leaves. It Values are expressed as mean ± standard error (n = 3). Journal of Agricultural and Food Chemistry Article 7649 dx.doi.org/10.1021/jf300459b | J. Agric. Food Chem. 2012, 60, 7644−7651 can also be used as a possible reference in estimating the dietary intake and adequacies of vitamins from microgreens. However, since growing, harvesting, and postharvest handling conditions may have a considerable impact on the synthesis and degradation of phytonutrients, including vitamins and carotenoids, additional studies may be needed to evaluate the effect of these agricultural practices on phytonutrient retention.
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